This invention relates to a tone signal processing device suitable for use in resampling a tone signal which has been sampled once with a sampling frequency of a relatively high rate with a sampling frequency of a lower rate.
An electronic musical instrument which has overcome the problem of an aliasing noise produced in the sampling process by harmonizing the sampling frequency of a tone signal to be generated with the pitch of the tone signal is well known as a pitch synchronous type electronic musical instrument. An example of such pitch synchronous type electronic musical instrument is disclosed in Japanese Preliminary Patent Publication No. 171395/1982 (particularly FIG. 5).
Since in this type of electronic musical instrument the sampling frequency is different for each note, the frequency of a basic sampling clock used commonly for establishing the respective sampling frequencies must be the least common multiple of these sampling frequencies, which naturally becomes a fairly high frequency (e.g., 800 kHz).
The fact that the sampling frequency of a tone signal generated by the pitch synchronous type electronic musical instrument is of a high rate gives rise to the problem that the sampling frequency is too high when this device is applied to a device such as a digital effect device which operates with a clock frequency of a lower rate. Hence an arrangement is made so that a digital tone signal supplied with a high frequency is resampled with a lower rate of frequency and the digital tone signal thus converted to a digital signal of the lower rate frequency is applied to a digital effect circuit. In this arrangement, however, there arises the problem that high frequency components contained in the original tone signal of the high-rate sampling frequency appear as an aliasing noise with respect to the low-rate sampling frequency.